Users expect an easy, quick and powerful experience whenever they use the latest electronic devices—and they want the same in their business lives. The user continues to demand a richer communication experience, especially users who are increasingly mobile or remote. It is desirable to provide access to content and services to a user away from the user's office or home, and on multiple devices. Businesses are increasingly deploying (or allowing) the use of smartphones and tablets. This deployment is largely served by Long-Term Evolution (LTE) technology. However, service providers continue to provide the other RATs. Thus, it would be desirable to enable user equipment (UEs) and tablets to select the best services and RATs among the available services and RATs quickly and with low power consumption. Users will not be able to use the best services if the users' devices select an inferior RAT. This may result in inefficient use of technology and resources impacting sales for both UE and network vendors and reducing the quality of user experience. In view of the above, a new algorithm is presented below to quickly select the best possible RAT once the device is powered on or out of coverage/roaming.
In traditional procedures, when a UE is switched on, an RPLMN RAT is selected based on access technology (AccTech) information saved in a User Services Identity Module (USIM) card or a non-volatile memory (e.g., flash memory) in the UE. However, even using a flash memory with valid AccTech, it is possible that a UE might select a lower priority RAT. Selection of a lower priority RAT could occur due to reselection/redirection/handover to a lower priority RAT in the most recent power on cycle as the flash memory will be updated or due to fall back to third generation (3G) or second generation (2G) of wireless mobile telecommunications technology during Circuit Switched FallBack (CSFB) call procedures and subsequent power off.
According to conventional procedures, a RAT is selected as follows. If during the most recent power on/off cycle, the UE selects a lower priority RAT, the lower priority RAT will be selected for a network search in the next power on cycle. For example, suppose the user is currently located in an area where only a 2G/3G network is available and the UE switches off or goes into flight mode. When the user moves to an area where a fourth generation (4G) of wireless mobile telecommunication technology network is available and switches on the UE, then by conventional procedures, the lower priority RAT that is either 2G or 3G will be selected for a network search in the next power on cycle. The UE will then switch to 4G through an Inter-Radio Access Technology (IRAT) procedure which may take more time.
Conventional UEs may save the RPLMN AccTech in flash memory and use it in the next power on. However, when the Subscriber Identity Module (SIM) card is changed, the UE uses the RPLMN AccTech of the previous SIM. In another case, a UE might detect the SIM change and avoid using the RPLMN AccTech from the flash memory but rather follow the priority order LTE>3G>2G. Following this priority order may delay UE registration during recovery or power on. The challenge discussed above may be observed in Dual SIM Dual Standby (DSDS) devices during SIM swap. Even though the new SIM has the ability to register on a higher priority RAT, the DSDS device will select a lower priority RAT. Since DSDS devices use a single radio-frequency (RF) resource (e.g., RF transceiver), reselecting a higher priority RAT may be further delayed based on activity on the other SIM.
In view of the foregoing, it would be desirable to provide methods which enable the UE to select the best registered public land mobile network (RPLMN) radio access technology (RAT) mode in wireless communication devices.